The present invention relates generally to electronic digital microcomputers and more specifically to a method for operating a microcomputer to present data damage caused by power outage.
Digital microcomputers are finding extensive use in many applications for various purposes. For example, in automotive applications, digial microcomputers are used for controlling operation of an engine at optimum conditions to meet emission standards and to achieve fuel economy. One problem with digital microcomputers is that if a microcomputer power supply is disconnected or fails, the data stored in the microcomputer storage mediums are destroyed. In automobiles this is a problem when the wet cell battery fails or is removed from the vehicle for recharging of failure. Although the use of nonvolatile memories can avoid the destruction of important data during power outage periods, such memories require a complex data transfer circuitry with a consequential unreliability and increase in cost. Another approach is to employ a complementary MOS memory which is powered exclusively from a trickle-charged power supply separate from the main battery. However, such a trickle-charged battery requires an additional maintenance effort to assure reliable operation.